In 2016, the warmest year on record, melting on the surface of the Greenland Ice Sheet began exceptionally early. Surface melt contributes to sea-level rise in two ways: excess water either runs off into the ocean or it flows through crevasses to the base of a glacier, temporarily speeding up the ice flow. Drag the vertical slider to see the difference in melting between June 10, 2014 (on the left) and June 15, 2016 (on the right).Photo:NASA Earth Observatory

In 2016, the warmest year on record, melting on the surface of the Greenland Ice Sheet began exceptionally early. Surface melt contributes to sea-level rise in two ways: excess water either runs off into the ocean or it flows through crevasses to the base of a glacier, temporarily speeding up the ice flow. Drag the vertical slider to see the difference in melting between June 10, 2014 (on the left) and June 15, 2016 (on the right).Photo:NASA Earth Observatory

Throughout your Senate confirmation hearings, and well before, you earned yourself the title of "climate denier" for your unwillingness to accept the science of climate change. Recently, though, you've made a rhetorical pivot. No longer can you outright deny that the planet is warming—the visible impacts of climate change are indisputable and such arguments are not credible. So now you’ve shifted your ever-doubting gaze on a different fact: that humans are responsible for climate change.

"I think that measuring with precision human activity on the climate is something very challenging to do and there's tremendous disagreement about the degree of impact,” you told CNBC yesterday, echoing a line from your Senate confirmation hearing. “So no, I would not agree that it's a primary contributor to the global warming that we see.”

Nice try, Scott, but you're still wrong. Let me walk you through it.

There is, in fact, ample evidence that carbon dioxide and other greenhouse gases, unleashed by fossil fuel-powered humans, are warming the planet. Back in the 1800s, scientists calculated that our planet should be colder than it is, considering its distance from the sun. They hypothesized that our atmosphere must contain some sort of insulation that traps heat and maintains a temperature toasty enough for life.

By the mid-1800s, they identified water vapor and carbon dioxide as potential heat-absorbing insulators and, by 1900, recognized that burning fossil fuels could increase their concentrations enough to warm the planet. And throughout the 1900s, we went ahead and combusted enough coal, oil, and gas to test this great hypothesis.

Just as those 19th-century scientists predicted, a more carbonated atmosphere caused the Earth’s temperature to rise. We know that the insulating carbon pollution comes from our energy sources because fossil fuel-based carbon carries a certain signature—a human signature—which increased in the atmosphere alongside our emissions. And we know that the same carbon pollution traps heat in the atmosphere, too; satellite measurements show that as insulating carbon pollution builds up in our atmosphere, less heat escapes to space. Thousands of observations and experiments performed by scientists around the world confirm these results.

There is very little argument about this. But the oil and gas industry manufactures a debate to avoid legal responsibility for their pollution and to eke out a few more years of profit and power. In response to the overwhelming scientific consensus, the industry has funded a massive pseudoscientific enterprise dedicated to denying the existence of global warming. Industry groups don’t have independent evidence to support their claims; if they did, we'd have heard about it long ago. Instead, their tactic is to assault the scientific process itself. They always demand more evidence, more certainty, and, crucially, more time.

You parrot these talking points when you insist that the evidence isn't yet firm enough to act—an insistence that goes against the basic demands of your job as EPA administrator. Our nation's environmental laws put public health before utmost certainty. If there's substantial evidence that a pollutant causes disease, for instance, the agency is expected to act to protect people before scientists identify the precise molecular pathways that lead to disease. Likewise, substantial evidence already exists that the climate is changing (see the above photo), and with ill effects. The agency shouldn't wait for science to precisely evaluate and predict those impacts before it acts. Indeed, with climate change, the only way to prevent the worst future scenarios is to address carbon emissions now, before it's too late.

That’s not to say that there isn’t debate to be had about what should be done about climate change. Uncertainty remains about how big the impacts will be, and how soon they will manifest. There are reasonable arguments about how quickly we should wean our civilization off of fossil fuels, and if we should stop using them altogether. There’s debate over how to prepare for and adapt to the coming threats, and how to protect the most vulnerable from the high-risk world brought on by global warming.

But you, Scott Pruitt, won’t let us have that conversation. You repeatedly pivot to attacks on foundational science instead of allowing real political debate about what to do about climate change. And in doing so, you demonstrate yet again that you put the profits of industry above the health of the American people and the wildlife under our care.